Heart failure occurs in nearly 5 million people a year in the U.S. alone at a combined cost of about $40 billion annually for hospitalization and treatment of these patients. The results of all the effort and cost are disappointing with a 75% five year mortality rate for the heart failure victims. Treatments for chronic heart failure include medical management with pharmaceutical drugs, diet and exercise, transplantation for a few lucky recipients, and mechanical assist devices, which are costly and risk failure and infection. Thus the landscape for cardiac treatment is turning in recent years to transplantation of tissue or cells.
Medical researchers have transplanted human hematopoetic stem cells, mesenchymal stem cells, endothelial precursor cells, cardiac stem cells, and skeletal myoblasts or bone marrow cells to the myocardium, with however little or mixed success in satisfactory regeneration of the myocardium. Another protocol involved injecting transforming growth factor beta preprogrammed bone marrow stem cells to the myocardium, with greater success than transplantation of bone marrow stem cells alone, but without generation of contractile myocardium.
After myocardial infarction, injured cardiomyocytes are replaced by fibrotic tissue promoting the development of heart failure. On the basis that embryonic stem cells may be directed to differentiate into true cardiomyocytes, transplantation of embryonic stem cells to a site of myocardial infarction may yield success in myocardial tissue regeneration, though the experiments have not yet so proven. For a related challenge, to induce angiogenesis in ischemic myocardial tissue, transplanting endothelial progenitor cells, with or without angiogenic protein factors has been proposed to generate capillary blood vessels at the site of ischemia in the myocardium. As yet, the experiments to prove these theories have not worked sufficiently to be attempted in humans.
Meanwhile, typical structural abnormalities or damage to the heart that would lend itself to tissue regenerative therapies, were they available, include atrial septal defects, ventricular septal defects, right ventricular out flow stenosis, ventricular aneurysms, ventricular infarcts, ischemia in the myocardium, infarcted myocardium, conduction defects, conditions of aneurysmic myocardium, ruptured myocardium, and congenitally defective myocardium, and these defective conditions remain untreated in humans by any current tissue regenerative techniques.
Although tissue regeneration has been accomplished by transplantation in mammalian tissues such as the endocranium, the esophagus, blood vessels, lower urinary tract structures, and musculotendinous tissues, heart tissue regeneration by foreign tissue explant has remained a challenge. Recently, myocardium has been regenerated using xenogenic extracellular matrix patches in pigs and dogs, and the contractility achieved was at 90% of normal.
It would be beneficial for treatment of heart failure in humans to develop myocardium regenerative strategies using matrices and additives for optimizing the potential results. One problem exists in the preparation of extracellular scaffolds in that they must be non-immunogenic and thus acellular before implantation. Getting rid of the cells in the matrix may also inadvertently strip the scaffold of key bioactive proteins. In order to perform procedures to regenerate human myocardium with fidelity, compositions that mimic the function of extracellular matrices are provided below.
No experimentation has been conducted to date on regenerating mammalian myocardium using an emulsified or injectable extracellular matrix formulation. The only known experimental use of extracellular emulsions for tissue regeneration have been with gastroesophageal repair to prevent reflux and urinary bladder sphincter repair. Both of these experiments were conducted in non-human animals. Some veterinary use of extracellular matrix emulsions have been reported, but none of those uses were for the repair of myocardium. The disadvantage of using intact, non-emulsified extracellular matrix compositions such as patches or strips is that placement of the material requires open surgery, with its coordinate risk of infection, challenge of access to the site, and longer recovery for the patient post-procedure.
The present invention pioneers compositions and alternatives to prior art solutions for tissue regeneration to provide a biomedical composition (and methods using the composition) for regenerating defective or absent myocardium, particularly for use in humans.